Re-measuring my new RB V8 UJ - 1.2415" or 31.5mm. Done more carefully than before, I have laid a white pencil in the bolt holes so it will be lying at the bottom of the hole i.e. the middle of the pencil should equate to the middle of the hole. One caliper finger is over the middle of the pencil, and the other is resting in the middle of the spider, as judged from the concentric rings on the end-face of the cup.

The Moss tool as received, showing the relative positions of the two holes.

Measuring from the tip to the centre of each hole 1.755" or 44.58mm ...

... and 1.151" or 29.24mm

About 1/8" misalignment when checked ...

... and after correction

Mid-era UK column: The column outer clamps A and B, and the concertina tube seal C. A also allows up and down movement for column UJ alignment, and when the two nuts on top of the heater shelf are slackened the whole bracket and clamp assembly B will slide from side to side for horizontal alignment.